Phenotypic Heterogeneity in Mitral Valve Prolapse: Insights from a Case Series.

Mitral valve prolapse (MVP) is the most common valvular heart disorder and shows marked phenotypic heterogeneity, ranging from benign forms to malignant variants associated with ventricular arrhythmias (VA), mitral annular disjunction (MAD), myocardial fibrosis, and sudden cardiac death (SCD). We present a case series of three patients with bileaflet MVP and mild mitral regurgitation (MR), followed longitudinally for more than a decade. Clinical assessment, electrocardiography, advanced echocardiography, 24-h Holter monitoring, exercise testing, and cardiac magnetic resonance imaging were used to characterize structural, mechanical, and electrical features. Phenotypic variability was evident across the three patients. Case 1 showed progressive MAD (5.4 to 11.3 mm), significant left ventricular (LV) dilatation, marked systolic curling, and a high burden of premature ventricular contractions with non-sustained ventricular tachycardia (NSVT), despite the absence of late gadolinium enhancement (LGE). Case 2 developed mild LV dilatation, curling, and basal inferolateral LGE, with exercise-induced NSVT, whereas Case 3, despite a family history of SCD, showed progression to moderate MR but no MAD, curling, or LGE, and only limited arrhythmic activity. These cases illustrate the broad phenotypic spectrum of MVP and support the concept that this condition may involve valvular, annular, myocardial, and electrophysiological abnormalities. MAD, curling, and LGE appear to represent overlapping but potentially independent markers of arrhythmic risk. Multimodality imaging may therefore be valuable for comprehensive risk stratification, even in asymptomatic patients, as structural and electrical features can evolve over time.